1. Field of Invention
The present invention relates to a surface treatment technology. More particularly, the present invention relates to surface treatment for a salicide process.
2. Description of Related Art
An integrated circuit (IC) is produced by a very complicated process. Generally, the complicated process consists of several hundred processing steps, and last about one or two months. During IC production, engineers use many modern technologies and inventions. Because these modern technologies and inventions are advanced but expensive, the IC industry is a highly risky industry that needs enormous investment for support. For this reason, any simplification or combination for those processing steps contributes much to the cost and time reduction for the process as a whole.
Conventionally, the formation of titanium silicide is performed by depositing titanium onto a silicon substrate, followed by rapid thermal annealing (RTA). This titanium layer can be deposited by TiCl4-based CVD and silicidation is accomplished in situ during glue layer deposition. The process temperature for TiCl4-based Ti is as high as about 650xc2x0 C. while that of a conventional PVD Ti is only about 200xc2x0 C. Moreover, the PVD has a deposition rate which is typically several times higher than that of CVD. Therefore, the fast PVD facilitates cost reduction, while the slow TiCl4-based CVD has high thermal budget that leads to difficulty in controlling junction leakage.
FIG. 1 is a flow chart schematically illustrating a conventional salicide process and the pre-processing steps thereof. The figure shows nine processing steps comprising the above-mentioned PVD and amorphization. First, on a silicon substrate having a polysilicon gate thereon, step 110 is performed to form an oxide spacer on the sidewall of the polysilicon gate. Steps 125 and 102a. belong to an amorphization process 120, are performed to amorphize the polysilicon gate and the substrate surface. The amorphizing steps 125, 102a, performed in an ion implanter, have a purpose of accelerating the subsequent metal deposition on the substrate. After the amorphizing steps 125, 102a are performed, the surfaces of the substrate, the polysilicon gate and the oxide spacer are wet cleaned as shown in step 130.
After this wet cleanings 130, the substrate and the devices thereon are then conveyed from the ion implanter to a sputtering equipment. Step 145 and step 150a. belong to a sputtering process 140, are performed in this sputtering equipment. In step 145, the surfaces of the substrate, the polysilicon gate and the oxide spacer are dry cleaned by sputtered argon. In step 150a, the substrate is covered with a sputtered metal film. The processing steps 120, 130, 145, performed before the metal covering step 150a, serve as pre-treatment for a salicide process.
Then, in a first annealing step 150b, the metal film thermally reacts with the exposed substrate and polysilicon gate to form silicide films. Step 150c then selectively etches the unreacted metal from regions such as the oxide spacer. After the first annealing step 150b, the silicide films are typically in a high-resistance phase. For this reason, after the etch step 150c. a second annealing step 150d is then performed to transform the silicide films into the desired low-resistance phase.
The conventional salicide process and pre-treatment thereof total nine processing steps in all. In the processing steps, the amorphization steps and the sputtering steps should be separately performed in different equipment units, thereby increasing the process complexity. Furthermore, the pre-treatment for the salicide process comprises five processing steps, is also complex and therefore increases the process costs and time. To save process costs and time, there is a need for a method that can simplify or combine those processing steps.
The present invention is directed to a method for treating a silicon substrate. The silicon substrate is placed into a sputtering equipment. A sputtering step is performed to simultaneously dry clean and amorphize the silicon substrate surface by the sputtering equipment. A titanium film is deposited on the silicon substrate by the sputtering equipment.
In one embodiment of this invention, the titanium film is deposited at about 540xc2x0 C. by an ionized metal plasma (IMP) equipment.
In this present invention, the sputtering and the deposition steps are performed in the same chamber, thereby improving the wafer throughput.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.